1. Field of the Invention
This invention relates to orienting and positioning flat glass articles and, in particular, to the precise positioning of pattern cut pieces of glass within the tolerances necessary for a robot to locate the articles and remove them from the conveyor platform.
2. Description of the Technical Difficulties
The art of handling glass sheets teaches frames and mechanisms generally involving vacuum cups for transferring glass sheets from a conveyor or stack to a stack or conveyor, respectively. Some handling patents of that type disclose sheet orienting as well. In U.S. Pat. No. 4,200,420 a sheet orienting and transporting frame is disclosed which orients and transports sheets. U.S. Pat. No. 4,228,993 teaches a sheet orienting and transporting frame having slidable dogs mounted on an elongated arm for orienting the sheet and vacuum cups for transporting the oriented sheet.
There are patents which disclose positioning sheets on a moving conveyor. U.S. Pat. No. 3,498,441 discloses one such positioning device for conveyed articles in which a shaft mounted transversely over the conveyor belt provides a plurality of positioning fingers depending therefrom and positions the articles while the conveyor is in motion. U.S. Pat. No. 3,701,643 discloses a moving locating device for aligning and orienting moving glass sheets which includes a mechanism to move the glass in a direction transverse to the path of movement. U.S. Pat. No. 3,761,542 teaches conveyor apparatus with electrically actuated article orienting means to orient an article as it travels down a conveyor.
Moving end stops for handling sheets are disclosed wherein the end stops move into and out of the way to stop an advancing sheet. U.S. Pat. No. 3,218,066 discloses a process and apparatus for handling sheets of glass which provides moving end stops at a point relative to the glass sheet. U.S. Pat. No. 4,064,659 provides movable end stops on an apparatus for centering sheets of glass on a platform of a machine in which the sheet of glass is centered by a plurality of movable pins around the periphery of the sheet.
A further type of article orienting apparatus is disclosed in U.S. Pat. No. 3,216,551 in which an apparatus is provided for orienting articles which senses incorrect orientation and then actuates an overhead rotation mechanism having depending members which, in turn, rotate the article.
With the advent of industrial robots, and in particular the semi and fully articulated type, it has been found that much human manipulation of articles in manufacturing can be eliminated. Robots are well suited for the performance of a variety of dangerous or repetitive tasks. One such task, for example, is the lifting of articles such as pattern cut pieces of flat glass from a conveyor table and the placing of those articles in precise register with one or more glass edging machines. In order to accomplish the precise placement of the glass article in the glass edging machine, it is necessary that the article be presented to the robot, aligned, oriented and placed in a particular location. The exact article location can then be programmed into the robot controller. If each succeeding article is presented to the robot in precisely the same location and in the same orientation, the robot will be able to consistently perform its function of transferring the article to the glass edging machine.
Articles being presented to the robot often vary in size and shape as different products are constantly being produced. It would thus be necessary to reprogram the robot to provide a new reference point to which all succeeding articles of a particular type are positioned and oriented. One way to provide such a precise reference point is to unload the conveyor by a human worker who then places the articles in a specific location. Unfortunately, the exact placement by a human worker negates the advantage of using the robot.
Another possibility of article presentment would be to use existing devices for orienting articles moving on a conveyor, however; none of those devices provide sufficient precision of location and orientation. Those devices also use movable stop means and/or position the article "on the fly" while traveling along the conveyor thus creating the possibility for error. The article must be presented to the robot in the same precise location within 0.05 inches in any direction. The cost of providing a robot and robot program to so precisely locate different sized articles moving on a conveyor also negates the advantage of the robot.
In order to utilize a robot effectively, the robot arm must be provided with a free path to travel above the pick up point. The prior art devices generally rely upon carriages and transverse bridges with depending fingers to align the article on a conveyor. It would be difficult, if not impossible, to use such an alignment device that projected above the conveyor platform or workpiece, as the robot would not be able to avoid the alignment device.
Accordingly, it would be most advantageous to provide a conveyor platform glass sheet positioning apparatus which would allow precise positioning of various sized articles, while not having any of its operating parts above the platform to interfere with the movement of the robot arm. Furthermore, it would be advantageous to provide such a positioning apparatus which would be easily adjustable to different shaped and sized sheet glass articles. Such an apparatus should totally stop the article prior to robot pick up, be capable of positioning different shaped and sized articles, not interfere with robot removal, and should be easily adapted to conventional conveyors. The instant invention is directed toward all of these needs.